Crystallizer for the continuous casting of a metal product, and corresponding casting method

A crystallizer for continuous casting of a metal product, configured to cast the product at a casting speed between 6 m/min and 15 m/min, the crystallizer having a casting cavity, into which liquid metal is cast, defined by walls connected to each other in correspondence with edges and being provided with primary cooling means associated with said walls, wherein an upper level of the liquid metal defines a meniscus wherein said cavity has an octagonal-shaped cross-section with a distance between two opposite walls comprised between 110 mm and 220 mm, and length comprised between 500 mm and 1500 mm, and has a taper converging downward of the single type comprised between 0.8%/m and 1.5%/m or of the multiple or parabolic type comprised between 2%/m and 4%/m in the meniscus zone, and between 0.2%/m and 1.0%/m in a lower part of the crystallizer, and wherein said primary cooling means are configured to produce a thermal flow in correspondence with the meniscus greater than approximately 6 MW/m2 and up to 14 MW/m2, and with an average value comprised between 3 MW/m2 and 5.5 MW/m2.